This invention generally relates to pneumatic rotary tools and more particularly to an improved pneumatic rotary tool having a plastic housing and a variable torque design for efficient use of pressurized air.
The invention is especially concerned with a powered tool that rotates an output shaft with a socket for turning a fastener element such as a bolt or nut. Tools of this type are frequently used in automotive repair and industrial applications. Most pneumatic rotary tools comprise a metallic outer housing with multiple metallic internal parts. These tools are strong and durable due to their metallic construction, although the all-metal construction makes them both somewhat heavy and costly. Pressurized air flowing through the tool powers tools of this type. As the air expands within the tool, it induces motion of an internal motor, powering the tool.
It is an aim of tool manufacturers to provide a pneumatic rotary tool that is as durable as an all-metal tool, but employs portions formed from lighter materials, such as plastic, where appropriate to reduce the weight and cost of the tool. One difficulty in the design of such a tool is the reduced rigidity of plastic as compared with a strong metal, such as steel. For example, plastic components in passageways used to direct the pressurized air may deform under pressure. Such deformation may allow the pressurized air to prematurely escape the tool and thereby decrease the efficiency and/or the torque output of the tool.